A sorting and distributing system is to be understood as a technique for sorting (or assigning) article units in accordance with customers' orders at the second stage of order-picking, preferably dedicated to logistic centers having a high order-picking performance. In dependence on the technique and the article size used, sorting performances of up to 2,000 to 40,000 pieces an hour can be achieved. Such sorting and distributing systems are known in the prior art, and are particularly known under the term “sorter”. Among other things, the capability of (automatically) identifying the units, for example through bar codes or transponders (RFID), and the capability of conveying the articles are prerequisites for the use of a sorter.
Hereinafter, an article unit is to be understood as a smallest sales units or a smallest packing unit. An article is a (smallest) unit of an assortment of article, distinguishable by number and label. Many times, articles are designated as wares or goods as well.
Primarily, sorters are distinguished according to their principle of function, independent of their performances. Among other things, there are rotating arm sorters, sliding sorters, tilt-tray sorters, pop-up sorters, etc., in order to exemplarily mention only some of them.
Different articles can be fed automatically to different target positions through a sorter. For that purpose, typically a rotary conveyor is provided which communicates with the target positions. A target position is to be understood as a location at which different articles are brought together in accordance with a customer's order for being packed, for example, into a shipping cardboard box. However, for allowing each target position to be fed with the right article, it is required to know, where an article is located on the rotary conveyor.
With a tilt-tray sorter, the sorting good is conveyed by means of gravity into a target chute by tilting transport trays. The tilt trays are mounted on carts which are connected to each other in an articulated manner. Driving of the tilt trays is caused by a rotary conveyor means (e.g. a chain) or by driving carts (e.g. via linear motors). Goods having greater lengths can be sorted by occupying several trays. Tilt-tray sorters allow the sorting of a broad assortment of articles (e.g. luggage) as well. Rotary speeds of about 2.5 m/s and sorting performances of about 15,000 pieces an hour are achieved.
According to the prior art, the filling of such a tilt-tray sorter then typically happens in an automated manner. The sorting conveyor is fed with articles by means of a separate conveyor, wherein the articles are delivered to the sorting conveyor at specific feeding points via the separate conveyor. At the feeding point one recognizes, preferably automatically, for example by reading a bar code, which (type of) article is to be delivered to which tray. Due to this information, a superordinated control can then guide the article to a predetermined target position. As already mentioned above, sorting performance of about 15,000 pieces an hour can be achieved in such a manner.
However, there are economical sectors, such as the retail of costume jewelry, requiring a greater sorting performance. Tasks are known which require a sorting performance of up to 60,000 pieces an hour. This cannot be achieved by means of a completely automated sorter.
Beside completely automated sorter, in the prior art there are sorting and distributing systems known as well, where the sorting conveyor is loaded manually. In this context, articles are manually scanned by operators at the feeding points, and subsequently thrown, for example, into trays of the sorting conveyor. The trays as such have holes in their bottoms for determining from beneath the tray, by means of a light intensity measurement, whether or not an article was given into the tray. If an operator has scanned an article and if it is simultaneously determined that this article has been given into a specific tray, then a superordinated warehouse management computer (WMC) can guide this article to a target position.
Thereby, mistakes occur frequently. On the one hand, it is not always ensured that the throwing-in of an article into a tray is actually detected. The detecting of a thrown-in article is the more difficult the smaller the packing size is. This is particularly critical in the area of the costume jewelry industry, since there the articles are very small.
Since the trays are loaded manually, a speed by which the trays pass the feeding point might not be too high, because otherwise the operator occasionally throws an article accidentally into a tray which is already filled. In this case, the WMC would not recognize that the tray holds another article or holds any article at all. Further, this “mistake” could not be corrected since the sorting conveyor, as a rule, cannot be stopped.
As an alternative to the above-mentioned options for automatically order-picking articles, it is known to cause the operator to walk with an order-picking container through the storage (“man-to-ware” principle) in order to retrieve the individual article types of a customers' order manually from the storage. However, in this manner only a very small sorting performance can be achieved. An order-picking process in accordance with the “man-to-ware” principle cannot be realized with a bigger assortment of articles if the order-picking requirements are high (e.g. 50,000 pieces an hour), since, on the one hand, a lot of space for installing the entire assortment of articles in a storage, through which one can walk, is required, and, on the other hand, a lot of operators (1 person for each order) has to walk through the storage, who block each other ways eventually.